A known vehicle bumper apparatus is disclosed in JP2009-83529A (which will be referred to as Reference 1). In the vehicle bumper apparatus disclosed in Reference 1, a bumper reinforcement member (bumper reinforcement) formed in an elongated shape is mounted to side members of a vehicle body by crush boxes and is supported thereby. The bumper reinforcement member extends in a width direction of a vehicle (in a vehicle width direction). The crush boxes are crushed, for example, by a load in a front-rear direction of the vehicle (in a vehicle front-rear direction) and therefore absorb an impact energy generated by the load.
In the vehicle bumper apparatus disclosed in Reference 1, the bumper reinforcement member has a hollow cross section. In addition, an interior portion (a vehicle interior portion) of the bumper reinforcement member in the vehicle front-rear direction is formed so as to have an open cross section including an opening. Reinforcement members for restricting the opening of the bumper reinforcement member from being expanded are arranged at attaching portions (to which the crush boxes are attached) of the bumper reinforcement member so as to close the opening. According to such configuration of the vehicle bumper apparatus of Reference 1, the bumper reinforcement member is downsized in weight and the strength thereof (against load) is increased. However, the reinforcement members that are separate components from the bumper reinforcement member and the crush boxes need to be additionally applied to the vehicle bumper apparatus of Reference 1. As a result, weight and cost increases resulting from the addition of the separate components are unavoidable in the vehicle bumper apparatus of Reference 1.
A need thus exists for a vehicle bumper apparatus and a crush box of the vehicle bumper apparatus, which are not susceptible to the drawbacks mentioned above.